(a) Field of the Invention
The present invention relates to a switch controller, switch control method, and a power supply including a switch controller.
(b) Description of the Related Art
A converter may control switching operation of a power switch according to an input voltage generated by full-wave rectifying an AC input.
The converter generates an internal reference signal that depends on the input voltage, and controls the switching operation of the power switch by comparing the internal reference signal with a current flowing in the power switch. In further detail, the internal reference signal has a phase synchronized by the input voltage.
However, a triac dimmer may be used to control the amount of AC input supplied to a load. The triac dimmer passes only a part of the AC input according to a predetermined dimmer angle. The dimmer angle indicates a phase of an AC input passing through a dimmer.
FIG. 1 shows a result of an AC input passed through a triac dimmer according to a dimmer angle. FIG. 1 exemplarily illustrates a case that the triac dimmer angle is included in a range from 0 to 90 degrees and a case that the triac dimmer angle is included in a range from 90 to 180 degrees.
As shown in FIG. 1, when the triac dimmer angle is included in the range from 0 to 90 degrees, a phase between 0 to 90 degrees and a phase between 180 to 270 degrees among one cycle of the AC input may pass the dimmer as shown in AC_1.
Unlikely, when the triac dimmer angle is included in the range from 90 degrees to 180 degrees, a phase of 90 to 180 degrees and a phase of 270 to 360 degrees among one cycle of the AC input may pass the dimmer as shown in AC_2.
However, when an internal reference signal is generated using an input voltage that is full-wave rectified from the AC input passed through the triac dimmer as shown in AC_1 and AC_2, the input voltage and the internal reference signal may not be synchronized.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.